1. Field of the Invention
The present invention relates to a gateway system and a gateway method for line connection via a telephone system, and in particular to a gateway system and a gateway method that facilitate the holding of video conferences by using a plain old telephone system. More specifically, the present invention pertains to a gateway system and a gateway method that permit the use of a current PBX and a LAN to provide video conference capabilities for in-house conference participants, or for such participants and other participants outside.
2. Description of Related Art
As a result of current technical improvements, personal computers (PCs) are now in widespread use and are being employed to accomplish a variety of tasks. For example, PCs are now used as a communication tool in much the same way as are telephones. Further, PCs have now advanced beyond the stage where they were simply terminals to be employed for electronic mail and communication, and have become a medium for the transfer of information that involves, such transmission means as sound, videos, and graphics. By connecting PCs together to form a network, and to thus make possible the display of common data (e.g., the faces of the other persons on a line, drawings, and photographs) while the individuals on the line converse by means of the microphones and loudspeakers that are hooked up to the PCs, the remote conference (or video conference) capability is enabled.
There are several forms by which the PCs can be linked. As an example, an Integrated Services Digital Network (ISDN) is employed as a data transfer medium. The ISDN is a network, for the transmission of digital data, in which two channels, a voice transmission channel and a data transmission channel, are logically assigned to one communication line. The ISDN handles not only voice telephone transmission, but can also generally handle so-called multi-media, such as text, data, static images, and motion video images. It is possible to construct a video conference system by connecting a number of PCs to one ISDN. Considering the rate at which ISDNs are being installed (considering especially the in-house provision of ISDNs), however, an investment for new equipment may be required and may not be an optimal solution.
As another form for the linking of PCs, it is possible to transfer both voice data and computer data over a Local Area Network (LAN). When communication is accomplished by means of a LAN, however, buffering is performed by the PC to hold a predetermined amount of data and the data is then transmitted at one time. Accordingly, the transmission of voice data is also delayed for the time that is equivalent to the buffering period. In other words, real time processing is lost. Since a video conference system especially must transmit an enormous amount of image information data and since the traffic on the line is heavy, voice cutoff is a frequent occurrence.
Another form employed for linking the PCs involves the use of a Plain Old Telephone System (POTS). In this case, modems are attached to the individual PCs, and their physical connection to the POTS is accomplished by inserting a connector, such as an RJ11, into the modem. However, current modems are suitable only for outside telephone lines and not available for use with the extension lines that are internally provided in schools, companies, etc., because the interfaces for the Private Branch Exchanges (PBXs) that controls the connection of private lines vary from maker to maker. Therefore, even in an office that is equipped with extension telephones, (1) participants in an in-house video conference have to bypass a PBX and employ outside telephone lines to connect their PCs, or (2) have to have produced and to employ a modem that matches the in-house PBX. In the former case, although the PCs can be connected by using a commercially available modem, a new outside telephone line must be provided for every participant, even in an office that is equipped with a PBX. The equipment expenditures and the difference in the usage costs between extension telephone lines and outside telephone lines are very high. In the latter case, since a modem for an in-house PBX has to be developed and produced, this is not practical in view of the effort and costs that are involved.
In summary, taking into consideration both telephone system use costs and equipment costs, the employment of the plain old telephone system (POTS) facilitates the implementation of a video conference system at an earlier stage than does the employment of a high-performance ISDN. In this case, however, disadvantages remain.